Apple Watch 5 liquid damage

So, I was under the impression that the Apple Watch 5 was resistant ? My partner started swimming and wearing the watch as it recorded his swims, he was never in the pool for more then 20 mins at a time, after a few days his watch started playing up, screen won’t turn off and the crown doesn’t function properly, also the microphone doesn’t work anymore! So it looks like it’s got liquid damage?

I guess there’s no point trying to get it fixed by apple as it’s out of warranty and I doubt they’d cover for liquid damage if it was!

apart from buying a new one, is there a way it can be fixed? Thanks